1. Field of the Invention
This invention relates to electronic systems, and more particularly to power sharing methods and systems.
2. Description of the Related Art
Electronic devices which capture, create, store, manipulate and/or transfer digital music, sound, images, movies or other encoded data have become more prevalent with the advent of less-expensive semiconductor processing and increased consumer demand. Applications such as portable MP3 (Moving Picture Experts Group layer 3 standard) players, PDAs (electronic personal data assistants), digital cameras and digital voice recorders continue to gain popularity. The general trend for each of these electronic applications is toward miniaturization and improved battery management.
These are several products with advanced battery management. One such product provides for an early warning to critical systems when the power-supply voltage for the system begins to fail. The warning enables the system microprocessor to perform essential tasks before a hard reset must be issued to turn off the system due to low supply voltage. The company also advises that system shutdown may be accomplished using a single threshold voltage detector in combination with a delay timer for the reset signal to ensure that the system voltage supply remains valid long enough to complete the system shutdown routine. (See Maxim Integrated Products, Inc., Low Battery Monitor Delays System Shutdown, P. 1 (Jul. 9, 1998))
Another solution can be found in the MC33351A power management IC (integrated circuit) offered by ON Semiconductor Corporation (with headquarters in Phoenix, Ariz.). This IC features a programmable current level for individual battery cells and two P-channel MOSFET (metal oxide silicon field effect transistor) switches to interrupt the appropriate discharge path FET (field effect transistor) in the event a parameter is exceeded. (See On Semiconductor Unveils Power Management IC, Electronic Component News, ¶4–5 (Nov. 15, 2000)) The IC also provides for a shutdown delay once a threshold is exceeded for a discharge current limit (Id. at ¶5). Similar to the previously described solution, the IC is designed for laptop and other single microprocessor applications.